Vitamin B12 is associated negatively with anemia in older Chinese adults with a low dietary diversity level: evidence from the Healthy Ageing and Biomarkers Cohort Study (HABCS)

Objective The associations between plasma vitamin B-12 level and anemia under different dietary patterns in elderly Chinese people are poorly understood. We aimed to examine the associations between plasma vitamin B-12 levels and anemia under different dietary patterns in adults aged 65 years and older in nine longevity areas in China. Methods A total of 2405 older adults completed a food frequency questionnaire at the same time as a face-to-face interview. The dietary diversity score (DDS) was assessed based on the food frequency questionnaire, with the low DDS group referring to participants with a DDS score <= 4 points. Vitamin B-12 levels were divided into two groups of high (>295 pg/mL) and low (<= 295 pg/mL) with the median used as the cut-off point. Sub-analyses were also performed on older adults divided into tertiles of vitamin B12 levels: low (< 277 pg/mL), medium (277-375 pg/mL) and high (> 375 pg/mL) to study the association of these levels with anemia. Results Six hundred ninety-five (28.89%) of these people were diagnosed with anemia and had a mean age of 89.3 years. Higher vitamin B-12 levels were associated with a decreased risk of anemia (multi-adjusted OR, 0.59, [95% CI, 0.45 similar to 0.77] P < 0.001) in older adults with a low DDS, whereas no significant association between vitamin B-12 levels and anemia was found in older adults with a high DDS in a full-model after adjustment for various confounding factors (multi-adjusted OR, 0.88, [95% CI, 0.65 similar to 1.19], P = 0.41). Conclusion The relationship between vitamin B-12 levels and the prevalence of anemia was significant only when the level of dietary diversity in the older adults was relatively low. The dietary structure of the population should be taken into consideration in combination in order to effectively improve anemia status by supplementing vitamin B-12.